Abstract: With the rubber plantation and seasonal rain forest in Xishuangbanna of Southwestern China as test objectives, a comparative study was conducted on their litter input, soil total C and N contents, and seasonal changes of soil active C and N from 2006 to 2007. Comparing with seasonal rain forest, rubber plantation had lower amount of aboveground litterfall and higher amount of floor mass, reflecting the lower decomposition rate (turnover coefficient, K) of litters, and had higher C/N ratio of litters and soil, indicating that the organic matters in rubber plantation were more resistant to degradation. The surface soil total organic C, labile organic C, and microbial biomass C concentrations in rubber plantation accounted for 60%〖KG-*2〗-〖KG-*7〗70% of those in seasonal rain forest, and the soil NO3--N concentration and pH value in rubber plantation were lower than those in seasonal rain forest, indicating that the conversion from seasonal rain forest to rubber plantation decreased the C and N inputs from aboveground litterfall and the availability of soil C and N, and caused soil acidification. Moderate land management strategies for rubber plantations were needed to prevent the degradation of soil quality and to maintain the productive sustainability.

Key words: organic carbon density, organic carbon storage, large scale, soil database, Zhejiang.